Abstract
This paper proposes the design and characterization of microstructure optical fiber for gas sensing applications. The aim is to detect toxic and colorless gases over a wide transmission band covering 0.80 µm to 2.00 µm wavelength. Numerical investigation is carried out by using the finite element method (FEM). The numerical study shows that sensitivity of the proposed sensor is moderately increased by introducing four non-circular holes around the defected core of photonic crystal fiber and the confinement loss is also reduced. Furthermore, we confirm that increasing the diameter of central air core and size of the non-circular holes can improve the relative sensitivity and the confinement loss is reduced by increasing the diameter of air holes in the cladding. The enhancement of the relative sensitivity is more than 27.58% (0.1323 to 0.1688) at the wavelength λ=1.33µm that is the absorption line of methane (CH4) and hydrogen fluoride (HF) gases. The confinement loss of the fiber is 1.765×10-8 dB/m.
Highlights
Photonic crystal fibers (PCFs) consist of periodically arranged microscopic cylindrical air holes that run along the entire length of fiber [1]
A gas sensor based on hollow core PBGPCFs is proposed in [12, 14,15,16,17] to confine more light into the core which contains gas Article type: Regular
This paper shows the relative sensitivity diagram for both of the hexagonal and circular holes but the confinement loss curve is shown for circular holes only
Summary
Photonic crystal fibers (PCFs) consist of periodically arranged microscopic cylindrical air holes that run along the entire length of fiber [1]. In 2013, an evanescent wave based PCF with four non-circular large air holes in the cladding was proposed by Zhang et al [19] for gas sensing application It showed that non-circular holes nearest core region helps to increase the relative sensitivity and reduce the confinement loss due to very high air filling fraction of about 93%. In this paper, it proposes an optimum structure of prior PCF [18] by introducing four non-circular air holes instead of six hexagonal holes around a hollow high index GeO2-doped silica ring to increase the relative sensitivity and to decrease the confinement loss
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